1. Field of the Invention
The invention relates to disc transfer method applied to a disc drive apparatus for reproducing, for example, music information and map information recorded on a disc, disc-shaped information recording medium, and recording desired information on a disc. More particularly, the invention relates to a disc transfer guide apparatus that enables a disc to move linearly along a predetermined path irrespective of variations of the atmospheric temperature, and a disc transfer apparatus equipped with the guide mechanism.
2. Description of Related Art
Conventionally, a type of a disc transfer apparatus for loading a disc in a case and ejecting a disc out of the case has been known, in which a disc is transferred by clamping the disc between a slim feed roller and a guide plate made of a synthetic resin (for example, Patent Document 1: Japanese Patent No. 4312147).
In the guide plate, an inclined protruding thread that makes a disc slide in contact only with the edge of a disc is formed. In paragraphs [0028] to [0029] and FIGS. 1 and 4 of Patent Document 1, the guide plate (upper guide 13) is constructed as a strip-shaped single plate extending along the axial direction of the feed roller (rubber roller 10), and both longitudinal sides thereof are fitted and fixed to a mount base (clamp lever 14).
However, if both longitudinal sides of the guide plate formed of a single plate member are fixed to a particular mount base, the guide plate may deform due to thermal expansion under an environment in which the temperature is different from a room temperature (i.e. about 20° C.), for example under a high temperature in summer season. In this situation, the guide plate cannot transfer the disc because of thermal expansion. More specifically, in the situation which both longitudinal sides of the guide plate are fixed on a particular mount base, although the guide plate has the thermal expansion, the guide plate cannot extend. Therefore, the guide plate may be required of the replacement.
Then, a disc transfer guide mechanism shown in FIG. 1 which a protruding piece Ga formed at one longitudinal end of a guide plate G and fitted to a hole Ba formed in a mount base B, and the other end of the guide plate G is allowed to expand from the place, which the guide plate G is fixed due to thermal expansion is known.
However, in this type of guide mechanism, a disc transfer may not be carried appropriately because each inclination of the protruding threads Gb and Gb is changed separately on the one end of the guide plate G and the other end when the guide plate G expands due to thermal expansion.
More specifically as shown in FIG. 2, one side of a disc D (the left side in FIG. 14) may not be clamped by a feed roller R and the protruding thread Gb, or the clamping force may become non-uniform between the left and right sides so the disc D may wobble left and right in transferred.
As a general example, a member Gc is set on the guide plate G for centering the disc D on the central line, which the line expanding from the center of the disc D is orthogonal to the axis direction of the turntable. However, when the guide plate G expands due to thermal expansion as described above, the gap between the left side and the right side of the centering members Gc and Gc accordingly widens as shown in FIG. 2. Consequently, the centering function for the disc D is lost, and the center of the disc D cannot be positioned on the axis direction of the turntable. Even if the centering member Gc is provided separately from the guide plate G to prevent the problem, the following problem arises. When the guide plate G itself expands due to thermal expansion, the inclination of the protruding threads Gb and Gb change between the left and right sides. Moreover, the disc D starts to wobble left and right soon after the center of the disc D passes the position where there are the centering members Gc, Gc in ejected, as indicated by the dash-dotted lines in FIG. 3. Thus, the quality and grade of the apparatus must be lost.
There is another problem in used under a low temperature, for example in winter seasons or in a cold region. Although the guide plate tends to undergo thermal shrinkage, the shrinkage is restrained. Thereof the internal stress occurs.
Therefore, by the repeated used under a low temperature (i.e. in a winter season) and under a high temperature (i.e. in a summer season) in many years, the internal stress occurs repeatedly and thermal fatigue is occurred. And the possibility of the adverse effects, such as causing cracks in the guide plate by the resulting thermal fatigue, cannot be ruled out.
In addition, since synthetic resin generally become brittle (i.e., embrittle) under a low temperature, there is a possibility of damages that are cracks caused by the internal stress originating from very small deformation under room temperature which no trouble may arise.
That is, due to the temperature variation of using environment compared with normal room temperature, the guide plate is placed under a load that can lead the guide plate to deformation or damages.